HVSR estimation of site effects in Melilla (Spain) and the damage pattern from the 01/25/2016 Mw 6.3 Alborán Sea earthquake

The January 25, 2016, Mw 6.3 Alborán Sea earthquake shook the autonomous city of Melilla (Spain) with a macro-seismic intensity of VI (EMS-98). In spite of this low intensity, significant non-structural damages were reported, whose cost was estimated in more than 13 million euros. The damages were concentrated in the modernist district, which is considered the most important and valuable part of the city. This scenario is not new in Melilla, since historical and instrumental seismicity studies based on intensities felt in Melilla have revealed that earthquakes with intensities of V–VI have a return period of approximately 25 years. However, seismic microzonation studies have not been carried out so far. In this paper, we present a seismic microzonation study based on seismic noise measurements and the foreshock, mainshock and aftershock records of the January 25, 2016, earthquake. The seismic signals were processed using the horizontal-to-vertical spectral ratio (HVSR) technique. The frequency amplification results were correlated with geological formations, and after that they were correlated with the distribution of damages. The lagoon and the recent alluvial deposits show the maximum number of damaged buildings and maximum frequency amplifications of 2–8 between 2 and 7 Hz. In the coastal deposits, some amplification in the same frequency range has been observed, but other formations show a minimum number of damaged buildings and a flat spectral response ratio. Two important factors in this damage pattern are the high vulnerability of ornamental facades characteristics (non-structural elements) of the modern architecture buildings and their location on the lagoon and the recent alluvial deposits where maximum site amplification is reached.

     

Speciation and Kinetics of Trihalomethane Formation in Drinking Water in Mexico

Water chlorination continues to be one of the most common water disinfection processes, especially in developing countries. When natural organic matter (NOM) is present, the process produces disinfection by-products (DBPs), some of them being trihalomethanes (THMs). This study determined the presence, speciation, and kinetics of THMs formation in the water supply for the northern area of the city of Toluca, Mexico. The results show that the concentrations of THMs are below the maximum allowable limits of 200 μg/L in accordance with NOM-127-SSA1-1994. Regarding THMs speciation, the presence of chloroform was more frequently observed in domestic water; furthermore, in one sample in which bromoform was present, it dominated over the chlorine species. Regarding the kinetics of THMs formation, a maximum concentration of THMs (THMs_Max) of 13.02 μg/L was obtained, and the time required to reach 50% THMs_Max ( t ₅₀) was 39.45 min.     

Turbulence Reynolds number and the turbulent kinetic energy balance in the atmospheric surface layer

The relation between the turbulence Reynolds numberR and a Reynolds numberz* based on the friction velocity and height from the ground is established using direct measurements of the r.m.s. longitudinal velocity and turbulent energy dissipation in the atmospheric surface layer. Measurements of the relative magnitude of components of the turbulent kinetic energy budget in the stability range 0 >z/L 0.4 indicate that local balance between production and dissipation is maintained. Approximate expressions, in terms of readily measured micrometeorological quantities, are proposed for the Taylor microscale and the Kolmogorov length scale .     

Periodic signals in Spanish monthly precipitation data

Summary Forty-two monthly rainfall time series from Spain have been analyzed for the presence of cycles and regional patterns. The study was carried out by means of periodicity tests devised by Whittle, Hannan, Bartlett, Siegel, and Priestley. These tests contribute to a mixed spectrum analysis leading to the evaluation of signals versus the background of coloured noise (autocorrelation). Also, a direct maximum entropy method (MEM) for estimating spectra was applied to the series, in particular an autoregressive (AR) power spectral density (psd) estimation, and an autoregressive moving average (ARMA) psd estimation, with parameters obtained by exact maximum likelihood estimator (MLE).With 4 Figures     

Towards an Automated Comparison of OpenStreetMap with Authoritative Road Datasets

OpenStreetMap (OSM) is an extraordinarily large and diverse spatial database of the world. Road networks are amongst the most frequently occurring spatial content within the OSM database. These road network representations are usable in many applications. However the quality of these representations can vary between locations. Comparing OSM road networks with authoritative road datasets for a given area or region is an important task in assessing OSM's fitness for use for applications like routing and navigation. Such comparisons can be technically challenging and no software implementation exists which facilitates them easily and automatically. In this article we develop and propose a flexible methodology for comparing the geometry of OSM road network data with other road datasets. Quantitative measures for the completeness and spatial accuracy of OSM are computed, including the compatibility of OSM road data with other map databases. Our methodology provides users with significant flexibility in how they can adjust the parameterization to suit their needs. This software implementation is exclusively built on open source software and a significant degree of automation is provided for these comparisons. This software can subsequently be extended and adapted for comparison between OSM and other external road datasets.     

Antigorite equation of state and anomalous softening at 6 GPa: an in situ single-crystal X-ray diffraction study

The compressibility of antigorite has been determined up to 8.826(8) GPa, for the first time by single crystal X-ray diffraction in a diamond anvil cell, on a specimen from Cerro del Almirez. Fifteen pressure–volume data, up to 5.910(6) GPa, have been fit by a third-order Birch–Murnaghan equation of state, yielding V ₀ = 2,914.07(23) Å³, K _T0 = 62.9(4) GPa, with K′ = 6.1(2). The compression of antigorite is very anisotropic with axial compressibilities in the ratio 1.11:1.00:3.22 along a, b and c, respectively. The new equation of state leads to an estimation of the upper stability limit of antigorite that is intermediate with respect to existing values, and in better agreement with experiments. At pressures in excess of 6 GPa antigorite displays a significant volume softening that may be relevant for very cold subducting slabs.     

The pulsational behaviour of the rapidly oscillating Ap star HD 122970 during two photometric multisite campaigns

We undertook two time-series photometric multisite campaigns for the rapidly oscillating Ap star HD 122970. The first one, conducted in 1998, resulted in 119 h of data and in the detection of three pulsation frequencies. The presence of possible further modes which held the promise of deriving a mode identification motivated a second worldwide campaign in the year 2001. This second campaign resulted in 203 h of measurement, but did not reveal further modes. Rather, one of the previously detected signals disappeared. The two modes common to both data sets have different spherical degree. They also showed slight frequency modulation, and one of them varied in amplitude as well. Possible causes of the latter behaviour include intrinsic instability of the pulsation spectrum or precession of the pulsational axis and orbital motion in a binary system. Frequency analysis of the Hipparcos observations of the star did not allow us to determine the stellar rotation period. The amplitude and phase behaviour of the two modes of HD 122970 in the Strömgren uvby bands is quite similar to that observed for other roAp stars.     

In situ Re–Os isotopic analysis of platinum-group minerals from the Mayarí-Cristal ophiolitic massif (Mayarí-Baracoa Ophiolitic Belt,eastern Cuba): implications for the origin of Os-isotope heterogeneities in podiform chromitites

Chromitite pods in the Mayarí-Cristal ophiolitic massif (eastern Cuba) were formed in the Late Cretaceous when island arc tholeiites and MORB-like back-arc basin basalts reacted with residual mantle peridotites and generated chromite-rich bodies enclosed in dunite envelopes. Platinum-group minerals (PGM) in the podiform chromitites exhibit important Os-isotope heterogeneities at the kilometric, hand sample and thin section scales. ¹⁸⁷Os/¹⁸⁸Os calculated at the time of chromitite crystallization (~90 Ma) ranges between 0.1185 and 0.1295 (γOs = −7.1 to +1.6, relative to enstatite chondrite), and all but one PGM have subchondritic ¹⁸⁷Os/¹⁸⁸Os. Grains in a single hand sample have initial ¹⁸⁷Os/¹⁸⁸Os that spans from 0.1185 to 0.1274, and in one thin section it varies between 0.1185 and 0.1232 in two PGM included in chromite which are only several millimeters apart. As the Os budget of a single micrometric grain derives from a mantle region that was at least several m³ in size, the variable Os isotopic composition of PGM in the Mayarí-Cristal chromitites probably reflects the heterogeneity of their mantle sources on the 10–100 m scale. Our results show that this heterogeneity was not erased by pooling and mingling of individual melt batches during chromitite crystallization but was transferred to the ore deposits on mineral scale. The distribution of the Os model ages calculated for PGM shows four main peaks, at ~100, 500, 750 and 1,000 Ma. These variable Os model ages reflect the presence of different depleted domains in the oceanic (Pacific-related) upper mantle of the Greater Antilles paleo-subduction zone. The concordance between the age of crystallization of the Mayarí-Cristal chromitites and the most recent peak of the Os model age distribution in PGM supports that Os in several grains was derived from fertile domains of the upper mantle, whose bulk Os isotopic composition is best approximated by that of enstatite chondrites; on the other hand, most PGM are crystallized by melts that tapped highly refractory mantle sources.     

Groundwater optimization model for sustainable management of the Valley of Puebla aquifer, Mexico

The Valley of Puebla aquifer (VPA), at the central region of Mexico, is subject to intensive exploitation to satisfy the urban and industrial demand in the region. As a result of this increased exploitation, a number of state and federal agencies in charge of water management are concerned about the problems associated with the aquifer (decline of groundwater table, deterioration in water quality, poor well productivity and increased pumping and water treatment costs). This study presents a groundwater management model that combines “MODFLOW” simulation with optimization tools “MODRSP”. This simulation–optimization model for groundwater evaluates a complex range of management options to identify the strategies that best fit the objectives for allocating resources in the VPA. Four hypothetical scenarios were defined to analyze the response of the hydrogeological system for future pumping schemes. Based on the simulation of flow with the MODFLOW program, promising results for the implementation of the optimization of water quantity were found in scenarios 3 and 4. However, upon comparison and analysis of the feasibility of recovery of the piezometric level (considering the policy of gradual reductions of pumping), scenario 4 was selected for optimization purposes. The response functions of scenario 4 were then obtained and optimized, establishing an extraction rate of 204.92 millions of m³/year (Mm³/year). The reduction in groundwater extraction will be possible by substituting the volume removed by 35 wells (that should be discontinued) by the same volume of water from another source.